摘要:

We have studied the variation of the Curie temperature &thgr;fand the spontaneous magnetization &sgr;sof several transition metals and some of their solid solutions as a function of the pressure. The measurements were carried out between 77° and 700°K. In the system Ni&sngbnd;Si,d&thgr;f/dpvaries from 0.32×10−3°K bar−1for pure nickel to 0.05×10−3°K bar−1for Ni‐9 at.% Si. The magnitude ofd&thgr;f/dpdecreases by 0.033×10−3°K bar−1per 1% of Si dissolved. In the system Ni&sngbnd;Cu,d&thgr;f/dpdecreases by 0.01×10−3°K bar−1per 1% of Cu dissolved. For polycrystalline cobalt, (&sgr;l)−1(∂&sgr;l/∂p), at 293°K, is equal to −10±1.5×10−7bar−1. The molecular field coefficient, representing the exchange integrals, increases for a decrease in volume in the case of Fe, Ni, Co, and the solid solutions Ni&sngbnd;Si, Ni&sngbnd;Cu, Fe&sngbnd;Si. The relative variation of the spontaneous magnetization with pressure is accounted for by the use of band theory.

ISSN:0021-8979    

DOI:10.1063/1.1714181

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The development of magnetic anisotropy induced by cold rolling of an alloy containing 90% Co—10% Fe was studied with the aid of torque curves and x‐ray texture data. In the annealed condition the texture is (31¯1¯) [112], and the torque dependence of the magnetization shows an easy direction both parallel and transverse to the rolling direction. As rolling proceeds to 98% reduction, the torque curves develop a sin2&thgr; dependence with the easy direction of magnetization transverse to the rolling direction. The torque maximum associated with the transverse direction, which is a measure of the stability of the rolling‐induced easy axis, develops linearly with true strain. The intensity of the x‐ray reflection from {110} planes lying in the plane of the sheet, which is a measure of the development of the rolled testure, also increases in a linear manner with true strain. At 98% or greater reduction, the texture becomes (11¯0) [335]. Theoretical torque curves computed on the basis of texture and the magnetocrystalline anisotropy energy give values for the first anisotropy constantK1, which compare favorably with the measured single‐crystalK1values, showing that the rolling‐induced anisotropy in this alloy is due principally to magnetocrystalline anisotropy energy.

ISSN:0021-8979    

DOI:10.1063/1.1714182

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A new alloy composed of 79.4% Ni, 16.6% Fe, 3.0% Nb, and 1.0% Ag has been developed for use in magnetic memory elements. After heat treatment the material in flattened‐wire form (0.003×0.00025 in.) has a rectangular hysteresis loop with a squareness ratio of 0.95, a coercive force of 1 Oe, and a switching coefficient of 0.3 Oe‐&mgr;sec. In basic Ni3Fe alloys, uniaxial magnetic anisotropy as well as increase in coercive force result from cold working. Normally, the anisotropy is destroyed by the anneal required to lower the coercive force. Retention of magnetic anisotropy has been achieved by the addition of Nb and Ag to the basic alloy. This behavior is attributed to the presence of dislocations anchored in the slip planes. These dislocations are believed to result from the interaction between lattice strains arising from the oversize foreign atoms (Nb and Ag) and strains generated by plastic deformation.

ISSN:0021-8979    

DOI:10.1063/1.1714183

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Previously, it was shown that oxygen is a factor in the magnetic annealing of Permalloy (Ni‐Fe alloys) and Perminvar (Ni‐Fe‐Co alloys). Electron‐diffraction studies indicated that oxygen caused impurity faults by condensing on the (111) planes of the crystal. An intimate connection between the presence of these impurity faults and the ability to respond to heat treatment in a magnetic field was established. However, the orientation of these faults was not observed to be directly related to the direction of the field heat treatment. In the present work on single crystals of 76% Ni—24% Fe, it was found that those crystals which were heat treated in a purified hydrogen atmosphere did not respond to the magnetic annealing treatments when cooled at normal rates, whereas those that were heat treated in a slightly oxidizing atmosphere did respond. Furthermore, after subsequent heat treatment, x‐ray investigations showed that the crystals which did not respond to magnetic annealing had substantially more long‐range ordering present (4 to 1) than the crystals which did respond. Long‐range ordering first appeared in both specimens after 475°C for 18 h. The specimens that did not respond to magnetic annealing also developed substantially higher values of crystal anisotropy than those that did respond. The uniaxial anisotropy which was developed by the slightly oxidized crystals could not be obliterated by ordering heat treatments. This work suggests that the oxygen inhibits the long‐range ordering mechanism, and, therefore, it may aid in the formation of like pairs of atoms.

ISSN:0021-8979    

DOI:10.1063/1.1714184

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A material combining low remanence with a low coercive force has been developed by applying a high‐temperature heat treatment to alloys in the region of 9 wt % aluminum iron. This material displays a large grain size with a predominantly (111) texture in the plane of the sheet. Epstein strips as well as rings of 9% aluminum iron had a remanence of 1.66 to 2.68 kG and a coercive force of 0.25 to 0.3 Oe. Other typical properties were a maximum permeability of 2700, inductions of 12.9 kG at 10 Oe and 16.1 kG at 100 Oe, electrical resistivity of 90 &mgr;&OHgr;‐cm, and Rockwell B hardness of 87. The properties of these alloys may be particularly suitable for application in relays, where a low residual induction would minimize or eliminate the air gap and good mechanical properties would reduce the wear of the relay pole faces.

ISSN:0021-8979    

DOI:10.1063/1.1714185

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Measurements of the decay of magnetic permeability with time after demagnetization have been performed on Fe—17 at.% Al. Measurements were obtained over the range of 360° to 475°C, with a wire specimen acting as the core of an open‐end transformer. The decay curves could be separated analytically into two components, with relaxation times differing by about a factor of six. Relaxation times for the shorter of the two components agree well with relaxation times calculated from observations of the Zener peak (by internal‐friction methods) in these alloys. Thus, as is the case for carbon in alpha‐iron, this component results from an ordering process which can be either stress or magnetically induced. The activation energy for this process is about 56 kcal/mole. The longer of the two relaxation processes apparently involves directional ordering alone.

ISSN:0021-8979    

DOI:10.1063/1.1714186

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The effect of pressure on the aluminum—manganese binary system was investigated by preparing various Al‐Mn alloys in a cubic multi‐anvil pressure apparatus. Pressures of 40 000 and 60 000 atm were used in preparing the alloys from powdered Al and Mn mixes. Indirect heating was used to melt the specimens and to apply a variety of heat treatments (including a magnetic anneal) to the alloys while they were under pressure. The x‐ray results indicate that pressures of 40 000 atm have little effect on the Al‐Mn system, since the phases prepared under pressure were the same as those found at 1 atm by other investigators of this system. A new identification of the phases present in the &eegr;, &eegr;′ region was made. One phase is body‐centered cubic (a0=8.9 Å), the other is face‐centered cubic (a0=12.5 Å). It was not possible to ascertain to which phase, &eegr; or &eegr;′, the abovea0values belonged. The results obtained at a pressure of 60 000 atm differed from those found at 40 000 atm as follows: (a) when quenching alloys in the 50–60 at. % Mn region from 1550°C at 60 000 atm, the magnetic &tgr; phase is formed in preference to the &egr; phase which is formed at 40 000 atm, and (b) a new phase, the structure of which is being determined, was formed from the &eegr;,&eegr;′ phases. Several specimen magnets were made by the high‐pressure technique; their magnetic properties were comparable to as‐cast AlMn magnets before they were given optimizing treatments.

ISSN:0021-8979    

DOI:10.1063/1.1714187

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Room‐temperature magnetoelastic waves have been observed in yttrium iron garnet from 1.6 to 8.5 Gc/sec. The minimum observed insertion loss, which includes conversion, transmission, and reconversion loss, was 15 dB at 1.6 Gc/sec; at 8.5 Gc/sec the smallest insertion loss was 46 dB. The transmission attenuation increases approximately linearly with frequency from about 6 to 20 dB/&mgr;sec over this frequency range. The experimentally observed conversion loss from electromagnetic to magnetoelastic energy ranges from 3 to 13 dB and is compared with theoretical values.

ISSN:0021-8979    

DOI:10.1063/1.1714188

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Experiments on electronically variable time delay of microwave pulses by transmission through single‐crystal YIG rods are discussed. One type of delay, recently discussed by Olson and Buchmiller and by Kaufman and Soohoo and attributed to magnetostatic waves, occurs with unpolished ends, has rapidly increasing delay with increasingHdc, and has severe pulse dispersion. The second, found here, requires parallel and polished ends, has a slowly decreasing delay with increasingHdc, and usually has at least two pulses spaced by less than the round‐trip time through the rod. Characteristics are similar to those described by Strauss, except that his experiments were of pulse reflection.The two aspects of magnetostatic wave pulse delay to be discussed are: (1) Additional experimental verification of Schlo¨mann's theory of wave excitation by nonuniform demagnetizing fields, by grinding a rod into ellipsoidal shape, and by measure coupling. (2) A nonreciprocal microwave time delay has been constructed utilizing magnetostatic waves in a YIG rod to couple two rectangular waveguides. The coupling is between the positions in the waveguide where the magnetic field is circularly polarized. The directionality of the coupling was found to be greater than 15 dB with delays of 4 &mgr;sec at 2500 Mc/sec.

ISSN:0021-8979    

DOI:10.1063/1.1714189

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A single‐pole, double‐throw, cutoff‐type ferrite switch has been developed for operation atC‐ andS‐band frequencies. TheC‐band unit is designed for a peak power level of 1 MW with an insertion loss less than 1 dB. Both units display a switching time of 150 &mgr;sec. The device consists essentially of a three‐port waveguide junction with a section of reduced size ferrite‐loaded waveguide at two of the ports. The characteristics of the reduced area sections are such that microwave energy in the frequency range of interest is propagated if no magnetic biasing field is applied. Upon application of the biasing field, the effective permeability of the ferrite is reduced, causing the loaded waveguide to be cut off. The structure is matched so that, if the magnetic field is applied to one section and not the other, a minimum input VSWR is obtained, and there is a maximum transfer of energy to the unbiased port. Switching is accomplished by applying the magnetic biasing field to one ferrite‐loaded section, while at the same time removing the magnetic field from the other. The technique of using cutoff waveguide to create the ``off'' condition provides isolation greater than that obtained by other means, e.g., switching circulators. It is believed that this is the first device of this type to be operated at a truly high power level. High‐power operation has been achieved by the novel approach of operatingabovethe onset threshold for subsidiary resonance absorption. This technique appears promising for use in the development of various high‐power devices in the future.

ISSN:0021-8979    

DOI:10.1063/1.1714190

出版商:AIP    

年代:1965

数据来源: AIP